The present invention relates to a heat sink for LSI package, etc., and more particularly, to an L-type (i.e., l-shaped pins) heat sink having a group of script's l(el)-shaped pinlike portions which is formed by a linear material with excellent heat transmission such as snaky capillary heat pipe with a small bore (hereinafter referred to as a capillary heat pipe).
One of previously proposed L-type heat sinks is disclosed in JP-A 5-21664 entitled "Wire Heat Sink and Method of Production thereof". This heat sink is constructed to have a number of needle-shaped pins embedded on a heat radiating side of a metal plate having heat receiving and heat radiating sides, and carries out effective heat radiation by using an effect of turbulent flow produced by the pins. Another conventional L-type heat sink is disclosed in JP-A 5-102357 entitled "Pin-type Heat Sink", which carries out effective heat radiation by using both an effect of turbulent flow and an effect of regular flow produced by rectangular ribbon pins.
Although each L-type heat sink has a heat radiation performance far greater than comparable conventional heat sinks of the plate-fin type, there remain the following problems to be solved in connection with the fundamental structure of integrating short wire pieces or ribbon pieces.
First, due to the structure of integrating short wire pieces or ribbon pieces, its assemblage necessitates a complicated manual work, resulting in a difficult reduction in a manufacturing cost.
Second, pressure loss is too great for cooling convective air passing between fins. The L-type heat sink includes pins having a thin diameter and wall for improving a heat radiation performance. However, in order to provide the high performance required by makers of the art, 450 pins need to be arranged on a radiating surface of 40 mm.times.40 mm, for example, resulting in increased pressure loss. In this example, when cooling convective air as fed at a front speed of 3 m/s or less flows out of the back, this speed lowers to 0.3 m/s due to pressure loss, which indicates a limit of the performance.
Third, even with either needle-shaped pins or rectangular ribbon pins, the weight may exceed a limit when being arranged at high density for obtaining a high performance. By way of example, when forming a heat sink having a heat receiving plate of 40 mm.times.40 mm and a fin height of 30 mm, and assuming a performance of temperature rise of 33.degree. C. or less at heat input of 40 W, i.e., heat resistance of 0.825.degree. C./W or less, the number of pure copper pins amounts to 320, and a total weight thereof amounts to 110 g. Since a desirable weight is 90 g or less for users, the requirement of decreasing the number of pins is produced even with a certain sacrifice of the performance.
Fourth, for obtaining a high performance, the pin diameter or the ribbon section needs to be fined or thinned to 0.8 mm, or 0.5 mm.times.1.4 mm. Thus, due to insufficient strength, the pins are easy to deform, so that finished L-type heat sinks should carefully be handled during application, packing for transport, etc.
Fifth, the structure adapts integrated short wire pieces or ribbon pieces, and does not use capillary heat pipes as long linear materials having excellent heat conductivity, resulting in a difficulty of further improvement of the performance.
It is, therefore, an object of the present invention to provide an L-type heat sink which contributes to improvement of a heat radiation performance without complicated manufacturing work. increased overall weight, increased pressure loss of cooling air, and reduced structural strength.